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United States Patent |
5,334,910
|
Karsten
,   et al.
|
August 2, 1994
|
Interlocking periodic permanent magnet assembly for electron tubes and
method of making same
Abstract
The present invention is a periodic permanent magnet (PPM) assembly used to
produce a focussing field within an electron tube, and the corresponding
method of manufacturing the same. The present invention PPM includes
producing two opposing semi-cylindrical stacks by alternately stacking
semi-annular shaped magnets and pole pieces. Once the two semi-cylindrical
stacks are formed, they are joined around the electron tube, such that the
various pole pieces and magnets of the two semi-cylindrical stacks align.
As a result of the joining of the two semi-cylindrical stacks, a
cylindrical periodic permanent magnet assembly is formed around the
electron tube in a cost effective and labor efficient manner.
Inventors:
|
Karsten; Kenneth S. (Bethlehem, PA);
Wertman; Richard C. (Allentown, PA)
|
Assignee:
|
ITT Corporation (New York, NY)
|
Appl. No.:
|
939306 |
Filed:
|
September 2, 1992 |
Current U.S. Class: |
315/5.35; 29/600; 335/210; 335/306 |
Intern'l Class: |
H01J 023/087 |
Field of Search: |
315/5.35
29/600,601,602.1
335/210,219,297,306
|
References Cited
U.S. Patent Documents
3221204 | Nov., 1965 | Hant et al. | 315/39.
|
3617802 | Nov., 1971 | Manoly | 315/3.
|
3644771 | Feb., 1972 | Kennedy et al. | 315/5.
|
3971965 | Mar., 1975 | Baker et al. | 315/3.
|
4392078 | May., 1983 | Noble et al. | 315/5.
|
4668893 | May., 1987 | Amboss | 315/5.
|
Foreign Patent Documents |
117052 | May., 1990 | JP | 315/5.
|
1020558 | Feb., 1966 | GB.
| |
Primary Examiner: Lee; Benny T.
Attorney, Agent or Firm: Plevy; Arthur L., Hogan; Patrick M.
Claims
What is claimed is:
1. A cylindrical periodic permanent magnet assembly through which a length
of an electron tube passes, comprising:
a plurality of annular pole pieces, wherein each of said plurality of pole
pieces is comprised of a first semi-annular member, having a male locking
projection extending therefrom, and a second semi-annular member having a
receptacle disposed therein, whereby the receptacle from each said second
semi-annular member receives the male locking projection from a
corresponding first semi-annular member thereby interconnecting each said
first semi-annular member to a corresponding second semi-annular member;
a plurality of ring magnets interposed with said plurality of annular pole
pieces such that each of said magnets is respectively juxtaposed between
adjacent ones of said plurality of said pole piece.
2. The periodic permanent magnet assembly of claim 1, wherein each of said
ring magnets is comprised of a first and second semi-annular magnet,
whereby each said first and second semi-annular magnets are alternately
disposed between corresponding ones of said first and second semi-annular
members respectively.
3. The periodic permanent magnet assembly of claim 2, wherein a magnet
retaining means is disposed on each of said first and a second
semi-annular members, said retaining means preventing the movement of each
said first and second semi-annular magnets from a set position between
corresponding ones of said first and second annular members.
4. The periodic permanent magnet assembly of claim 3, wherein each said
receptacle disposed in each said second semi-annular member permanently
retains a male locking projection from a corresponding first semi-annular
member therein, thereby preventing the separation of each said first
semi-annular member with each corresponding second semi-annular member.
5. The periodic permanent magnet assembly of Claim 4, wherein each said
receptacle includes a narrow slot region that terminates at one end with
an enlarged distal chamber having a rearward surface, each said male
locking projection passing into said slot region, contacting and deforming
against said rearward surface, as said first and second semi-annular
members interconnect, whereby the deformation of said male locking
projection prevents the retraction of said male locking projection through
said slot region, permanently joining corresponding first and second
semi-annular members.
6. The periodic permanent magnet assembly of claim 3, wherein each of said
pole pieces includes side surfaces that abut against the corresponding
ring magnets, and said retaining means includes a groove disposed on each
of said side surfaces of said pole pieces, wherein each said ring that
abuts against said groove passes into each said groove on said pole
pieces, each said groove thereby retaining said first and second
semi-annular magnet of a corresponding ring magnet in said set position.
7. A cylindrical periodic permanent magnet device for an electron tube,
comprising:
a first semi-cylindrical assembly of interposed first magnet members and
first pole pieces, wherein each of said first magnet members is
respectively juxtaposed between adjacent ones of said first pole pieces,
each of said first pole pieces having a respective locking member
extending therefrom; and
a second semi-cylindrical assembly of interposed second magnet members and
second pole pieces, wherein each of said second magnet members is
respectively juxtaposed between adjacent ones of said second pole pieces,
each of said second pole pieces having a respective receptacle disposed
therein for receiving and retaining a corresponding one of said locking
members from said first pole pieces, thereby interconnecting each said
first pole piece assembly to a corresponding said second pole piece
assembly such that each of said first magnet members and said second
magnet members align.
8. The periodic permanent magnet device of claim 7, wherein said electron
tube is a traveling-wave tube and includes a signal input and a signal
output supported by a first and second rigid flange, respectively, that
are a predetermined distance apart, said first semi-cylindrical assembly
and said second semi-cylindrical assembly having an overall length
corresponding to said predetermined distance between said first and second
rigid flange such that said first and second rigid flange confine said
first and second semi-cylindrical assembly around said traveling-wave
tube, thereby preventing the disassembly of said first and second
semi-cylindrical assembly.
9. A method of forming a cylindrical periodic permanent magnet assembly
around an electron tube, comprising the steps of:
providing a plurality of semi-annular shaped first pole pieces, each first
pole piece having a locking projection extending therefrom;
providing a plurality of semi-annular shaped first magnet members;
alternately stacking said semi-annular shaped first magnet members and said
semi-annular shaped first pole pieces thereby forming a first
semi-cylindrical assembly wherein each of said first magnet members is
respectively juxtaposed between adjacent ones of said first pole pieces;
providing a plurality of semi-annular shaped second pole pieces, each
second pole piece having a receptacle formed therein;
providing a plurality of semi-annular shaped second magnet members;
alternately stacking said semi-angularly shaped second magnet members and
said semi-angularly shaped second pole pieces thereby forming a second
semi-cylindrical assembly wherein each of said second magnet members is
respectively juxtaposed between adjacent ones of said second pole pieces;
placing said electron tube in between said first a semi-cylindrical
assembly and said second semi-cylindrical assembly; and
joining said first semi-cylindrical assembly to said second
semi-cylindrical assembly around said electron tube such that said first
magnet members and said second magnet members correspondingly align and
said first pole pieces and said second pole pieces correspondingly align
wherein each said locking projection on said first semi-cylindrical
assembly passes into a corresponding receptacle in said second
semi-cylindrical assembly thereby interconnecting said first
semi-cylindrical assembly to said second semi-cylindrical assembly.
10. The method according to claim 9, wherein each said receptacle has a
rear surface and said step of joining further includes deforming each said
male projection in each said receptacle by advancing the corresponding
male projection against the rearward wall of the corresponding receptacle,
thereby preventing the retraction of each said male projection from each
said receptacle.
11. The method according to claim 10, wherein said electron tube is a
traveling-wave tube and includes a signal input and a signal output
supported by a first and second rigid flange, respectively, that are a
predetermined distance apart and said step of alternately stacking shaped
first magnet members and shaped first pole pieces includes forming said
first semi-cylindrical assembly to have a length that corresponds to said
distance between said first and second rigid flange on said traveling-wave
tube and said step of alternately stacking shaped second magnet members
and shaped second pole pieces includes forming said second
semi-cylindrical assembly to have a length that corresponds to said
distance between said first and second rigid flange, on said
traveling-wave tube.
12. The method according to claim 11, wherein said step of joining includes
joining said first semi-cylindrical assembly to said second
semi-cylindrical assembly around said traveling-wave tube between said
first and second flange so that said first and second flange contact and
confine said first and second semi-cylindrical assembly thereby preventing
the disassembly of said first and second semi-cylindrical assemblies.
13. The method according to claim 12, wherein said step of alternately
stacking said first magnet members and said first pole pieces includes
positioning said first magnet members and said first pole pieces in a
first fixture that maintains said first magnet members and said first pole
pieces in a first desired orientation, and said step of alternately
stacking said second magnet members and said second pole pieces includes
positioning said second magnet members and said second pole pieces in a
second fixture that maintains said second magnet members and said second
pole pieces in a second desired orientation, wherein said step of joining
said first semi-cylindrical assembly to said second cylindrical assembly
occurs automatically as said first fixture is advanced against said second
fixture.
14. The method according to claim 13, wherein said step of joining further
includes compressing said first semi-cylindrical assembly and said second
semi-cylindrical assembly together thereby causing each said male
projection to contact and deform against a rearward surface in each
corresponding said receptacle, preventing each said male projection from
being retracted from the corresponding said receptacle.
Description
FIELD OF THE INVENTION
The present invention relates to a periodic permanent magnet assembly for
focusing an electron beam within an electron tube, and the corresponding
method of manufacturing the same. More particularly, the present invention
relates to periodic permanent magnet structures formed into two opposing
semi-cylindrical segments whereby an electron tube is positioned between
the opposed segments and the segments are joined in a manner that affords
magnetic continuity, thereby creating the desired permanent magnet
focusing structure in a labor and cost efficient manner.
BACKGROUND OF THE INVENTION
In electron tubes, such as traveling-wave tubes (TWTs), it is necessary to
provide a focusing field for the electron stream as it travels along the
tube, from the cathode to the collector. The focusing field, be it
magnetic or electrostatic, must be of a strength appropriate to overcome
the space-charge forces within the electron tube that would otherwise
cause the electron beam to spread. In the past a longitudinal magnetic
field was supplied along the length of the electron tube utilizing a
electromagnetic solenoid. However, the continuing demands for improved
efficiency and reliability, and for weight and size reduction, have
resulted in the development of periodic permanent magnet (PPM) structures.
As will be recognized by a person skilled in the art, PPM structures focus
the electron beam by periodically positioning magnets of opposite polarity
along the length of the electron tube, thereby creating a periodically
reversing magnetic field which acts to confine the passing electron beam.
Typically, in prior art PPM assemblies, a series of angularly formed pole
pieces, non-magnetic spacers and individual ring magnets are stacked on
top of one another to form an elongated cylinder in which a linear or
semi-linear electron beam device can be placed. In such prior art PPM
assemblies, the pole pieces and non-magnetic spacers are fabricated as
cylindrical sections, which are joined to create the overall cylindrical
shape of the PPM assembly. Typically, the ring magnets are formed as
semi-circles and are affixed to either side of the various pole pieces by
being either clamped, taped or glued into place. The process joining the
pole pieces to the non-magnetic spacers and affixing the ring magnets to
the pole pieces, results in an assembly procedure that is inefficient,
requiring excessive handling of the PPM assembly and long assembly time.
It is therefore a primary objective of the present invention to set forth a
PPM assembly and corresponding method that is both less expensive and less
labor intensive to assemble, thereby reducing the cost of manufacturing
the PPM assembly and reducing damage to the PPM assemblies caused by
excessive handling.
SUMMARY OF THE INVENTION
The present invention is a periodic permanent magnet (PPM) assembly used to
produce a focussing field within an electron tube and the corresponding
method of manufacturing the same. The present invention PPM includes
producing two opposing semi-cylindrical permanent magnet stacks by
alternately stacking semi-annular shaped magnets and pole pieces. Once the
two semi-cylindrical stacks are formed, they are joined around the
electron tube, thereby aligning the various pole pieces and magnets of the
two semi-cylindrical stacks. As a result of the joining of the two
semi-cylindrical stacks, a cylindrical periodic permanent magnet assembly
is formed around the electron tube in a cost effective and labor efficient
manner.
The semi-annular pole pieces used to form the first of the two
semi-cylindrical permanent magnet stacks, have a male locking member
extending from a face surface. Similarly, a corresponding receptacle-is
formed in the pole pieces used to form the second semi-cylindrical
permanent magnet stack. As the two semi-cylindrical stacks are joined, the
male locking members enter and become locked within, the opposing
receptacles, thereby permanently joining the first and second
semi-cylindrical stacks into the cylindrically shaped present invention
PPM.
Each of the semi-cylindrical stacks used to create the present invention
PPM are formed by the juxtaposition of semi-annular magnets between the
various semi-annular pole pieces. As will be recognized by a person
skilled in the art, magnets within a PPM assembly utilize alternating
magnets of opposite polarity. As such, the magnets within each
semi-cylindrical stack repel one another thereby resisting a stacked
orientation. To help hold each magnet into one set position within each
semi-cylindrical stack, a groove is formed on each side of the various
pole pieces. The grooves formed on the pole pieces correspond in shape to
the semi-annular magnets. As such, each magnet passes into the grooves
formed into the pole pieces, on either side of the magnet. Consequently,
the magnets become entrapped between the various pole pieces and are
restrained from moving when influenced by a repulsive magnetic force.
The repulsive magnetic forces created by the various stacked magnets tend
to push apart the semi-cylindrical stacks. Consequently, when the various
semi-cylindrical stacks are formed, the magnets and pole pieces are
stacked in a fixture that holds the stacks together. When the
semi-cylindrical stacks are joined around an election tube to form the
present invention PPM, the fixtures are removed. The present invention PPM
is formed so as to exactly span the electron tube in between the rigid
signal input port and rigid signal output port of the election tube. As
such, the present invention PPM spans the election tube between the signal
input port and the signal output port and is confined therebetween,
thereby presenting the present invention PPM from disassembling from the
repulsive forces of the component magnets.
The process of forming a PPM assembly around a prefabricated election tube,
by sandwiching the election tube between two semi-cylindrical permanent
magnet stacks, reduces both the cost and labor of producing electron tubes
with PPM assemblies.
BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of the present invention, reference is made to
the following description of an exemplary embodiment thereof, considered
in conjunction with the accompanying drawing in which:
FIG. 1 shows an exploded perspective view of one pole piece and
corresponding ring magnets from one exemplary embodiment of the present
invention periodic permanent magnet assembly;
FIG. 2 shows a cross-sectional view of the exemplary embodiment shown in
FIG. 1, viewed along section line 2--2;
FIG. 3 shows an isolated view of a preferred embodiment of locking
arrangement that joins the male and female halves of the pole piece of the
present invention;
FIG. 4a and 4b show an isolated view of an alternative embodiment for the
locking arrangement;
FIG. 5 shows a semi-cylindrical PPM stack subassembly formed by alternately
stacking semicircular pole piece segments and magnets so as to form half
the present invention PPM stack; and
FIG. 6 shows the means by which the present invention periodic permanent
magnet assembly is formed and positioned around a traveling-wave tube.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention is a periodic permanent magnet (PPM) assembly used to
produce a focusing field within a linear or semi-linear electron beam
device such as a traveling-wave tube (TWT). As will be recognized by a
person skilled in the art, PPM assemblies are typically cylindrical in
form, surrounding the path traveled by the electron beam. The present
invention periodic permanent magnet assembly is constructed by stacking a
plurality of semicircular magnets with flux guides, or pole pieces to
create a semi-cylindrical subassembly. The TWT, or other electron beam
device, is then positioned between two of the semi-cylindrical
subassemblies as they are joined, thereby creating the needed cylindrical
configuration.
In FIG. 1 there is shown one preferred embodiment of a pole piece 12 and a
corresponding ring magnet 14 that is used to construct the present
invention PPM. Referring first to the pole piece 12, it can be seen that
the pole piece 12 is constructed of two semicircular members, including a
first pole piece member 16 and a second pole piece member 18. The first
pole piece member 16 and the second pole piece member 18 being identical
in construction except for the presence of a male locking flange 20 on the
face surface 22 of the first pole piece member 16 and the presence of a
female receptacle 24 extending into the second pole piece member 18 from a
face surface 26 of the second pole piece member 18. As will later be
described, the male locking flange 20 of the first pole piece member 16
passes into the female receptacle 24 of the second pole piece member 18,
allowing the face surface 22 of the first member 16 to abut against the
face surface 26 of the second pole piece member 18, forming a single
circular pole piece 12.
Centrally positioned along the face surface 26 of the second pole piece
member 18 is a semicircular relief 30. Similarly, a semicircular relief 32
is centrally positioned along the face surface 22 of the first pole piece
member 16. When the first pole piece member 16 is joined to the second
pole piece member 18, the two semicircular reliefs 30, 32 align, thereby
creating a circular aperture concentrically positioned in the center of
the pole piece 12. Surrounding the semicircular relief 32 on the first
pole piece member 16 is an enlarged semicircular shaped hub 36. Similarly,
an enlarged semicircular shape hub 38 is also formed around the
semicircular relief 30 on the second pole piece member 18. The
semicircular hub 36 on the first pole piece member 16 aligns with the
semicircular hub 38 on the second pole piece member 18, as the first and
second pole piece members 16, 18 are joined, thereby creating an annular
hub concentrically positioned about the circular aperture, formed by the
joining of the two semicircular reliefs 30, 32.
Positioned about the periphery of the curved edge of the second pole piece
member 18 is an enlarged rim 40. The area between the semicircular hub 38
and the enlarged rim 40 has a reduced width, thereby giving the second
pole piece member 18 a substantially I-shaped profile. Consequently, a
semicircular channel 42 is formed on either side of the second pole piece
member 18, wherein the channel 42 is defined at one end by the presence of
the hub 38 and at the opposing end by the presence of the enlarged rim 40.
Similarly, the first pole piece member 16 also has an enlarged rim 44
positioned along its curved periphery, thereby giving the first pole piece
member 16 a substantially I-shaped profile. Therefore, a semicircular
channel 46 is formed on either side of the first pole piece member 16,
being defined by the presence of the hub 36 along one end and by the
presence of the enlarged rim 44 at the opposing end. When the first pole
piece member 16 and the second pole piece member 18 are joined, the
enlarged rim 40 of the second pole piece member 18 aligns with the
enlarged rim 44 of the first pole piece member 16, thereby creating a
continuous circular enlarged rim that circumvents the entire periphery of
the pole piece 12. Additionally, the semicircular channel 42 formed on
either side of the second pole piece member 18 aligns with the
semicircular channel 46 formed on either side of the first pole piece
member 16, thereby creating a continuous, angularly shaped channel on
either side of the pole piece 12.
The pole piece 12 is constructed of a ferromagnetic material and a ring
magnet 14 is joined to each pole piece 12. The ring magnet 14 is formed of
two identically shaped semicircular magnets 50, 52, that when combined
produce an annular shape. The first semicircular magnet 50 is dimensioned
so as to exactly fit within the semicircular channel 46 formed on the
first pole piece member 16 of the pole piece 12. Similarly, the second
semicircular magnet 52 is dimensioned so as to exactly fit within the
semicircular channel 42 formed on the second pole piece member 18 of the
pole piece 12. Consequently, when the first and second pole piece members
16, 18 of the pole piece 12 are joined, a continuous ring magnet 14 is
formed, held against the pole piece 12 by magnetic force. The presence of
the ring magnet 14 in the channel of the pole piece 12, positions the ring
magnet 14 between the central hub and the peripheral enlarged rim, thereby
restricting the radial movement of the ring magnet 14 on the pole piece
12.
As has been previously described, a male locking flange 20 extends from the
face surface 22 of the first pole piece member 16. The male locking flange
20 is not continuous, but rather is divided in the region of the
semicircular relief 32. On the face surface 26 of the second pole piece
member 18, a female receptacle 24 is formed so as to allow for the passage
of the male locking flange 20 therein. Referring to FIG. 2 it can be seen
that the male locking flange 20 is unistructurally formed as part of the
first pole piece member 16, as such the male locking flange 20 is formed
of the same ferromagnetic material as is the first pole piece member 16.
The female receptacle 24 is formed as a slot 56 cut from the material of
the pole piece second member 18. The slot 56 has a width W that is
slightly larger than the thickness of the male locking flange 20. The slot
56 terminates, within the second pole piece member 18, at an enlarged
chamber 58 that has a width larger than the width W of the formed slot 56.
The overall depth of the slot 56 and enlarged chamber 58 is less than the
length L of the male locking flange 20. As the first pole piece member 16
and second pole piece member 18 are joined, the male locking flange 20
enters the female receptacle 24. Since the overall depth of the female
receptacle 24 is less than that of the length L of the male locking flange
20, the male locking flange 20 contacts the rear wall 60 of the female
receptacle 24, before the face surface 22 of the first pole piece member
16 abuts against the face surface 26 of the second pole piece member 18.
Referring to FIG. 3 in conjuncture with FIG. 2, it can be seen that the
rear wall 60 of the female receptacle 24 is not flat, but rather is curved
relative to the approach of the male locking flange 20 through the slot
56. Consequently, when the male locking flange 20 is driven into the
female receptacle 24 by compression force F (as designated by the arrows
in FIG. 3), the male locking flange contacts the rim wall 60, the male
locking flange 20 is deformed along the curve of the wall 60. The male
locking flange 20 is therefore deformed in the confines of the enlarged
chamber 58. Once deformed, the male locking flange 20 is blunted and
consumes more space than it did in its undeformed state. The male locking
flange 20 is deformed into a configuration that is larger than the width W
of the slot 56 segment of the female receptacle 24. Consequently, the male
locking flange 20 cannot be withdrawn through the slot 56 and the male
locking flange 20 is permanently locked within the female receptacle 24.
In FIG. 4a and FIG. 4b, an alternative embodiment of the female receptacle
24 is shown wherein the slot 56 of the female receptacle leads into two
enlarged chambers 62, 64. Each of the two enlarged chambers 62, 64 having
an opposed sloped rear wall 61, 63. The male locking flange 65 then
deforms into both enlarged chambers 62, 64. The male locking flange 65 is
split down the middle. As such, when the male locking flange 65 is
deformed by compression force F (as designated by the arrows in FIG. 4a)
against the rear walls 61, 63 each half of the male locking flange 65
deforms into an enlarged chamber 61, 63 in the manner previously
described.
Regardless of whether the embodiment of FIGS. 3 or 4a are used, it should
be recognized that the coupling of the male locking flange into the female
receptacle is done so in a manner that promotes metal to metal contact
between the first pole piece and second pole piece members 16, 18, thereby
promoting magnetic continuity across the entire pole piece 12 when
assembled. Furthermore, it should be recognized by a person skilled in the
art that there exist many varied techniques to join male flanges into
female receptacles. Such techniques may include, but are not limited to,
the formation of a locking pawl on the male flange or an interference fit
between the male flange and the female receptacle. The shown embodiment of
a deformable male locking flange 20 is merely exemplary, being the best
contemplated mode for effectively and inexpensively joining the first and
second pole piece members 16, 18 of the pole piece 12, however, in the
alternative any known joining method can be used.
As has been previously stated, the present invention PPM assembly is
comprised of a plurality of pole pieces 12 and ring magnets 14 being
alternatively stacked atop one another, surrounding an electron beam
device. As will be recognized by a person skilled in the art, alternate
magnets present in a PPM assembly have reversed faced poles so as to
provide periodically reversing magnetic fields along the length of the
electron beam device. Referring to FIG. 5, there is shown a
semi-cylindrical permanent magnet subassembly 70 being formed by
alternatively stacking second pole piece members 18 with its corresponding
semicircular magnet 52.
As can be seen, each second pole piece member 18 is coupled to two adjacent
magnets 52. However, in the preferred embodiment, each of the magnets 52
contact the second pole piece member 18 with a common pole, either
negative (-) or positive (+). Consequently, each magnet 52 is repelled
from each second pole piece member 18 by the force of the magnet on the
opposite side of the second pole piece member 18. As the second pole piece
members 18 are alternatively stacked with the magnets 52, the semicircular
hubs 38 of adjacent second pole piece members 18 and the various
semicircular reliefs 30 align so as to form a periodic semicircular relief
73 that travels the length of the permanent magnet subassembly 70. Between
each semicircular hub 38 exists a gap 72, wherein the gaps 72 are formed
by the width of the magnets 52 as compared to the depth of the channels 42
formed in each of the hubs 38. The channels 42, formed on either side of
each second pole piece member 18, are dimensioned so as to confine the
magnets 52 as the second pole piece members 18 are stacked. Consequently,
each magnet 52 becomes confined between the channels 42 of two adjacent
second pole piece members 18, as the second pole piece members 18 and the
magnets 52 are alternatively stacked. As can be seen from FIG. 5, each
channel 42 contacts three surfaces of a magnet 52. As such, the presence
of the hub 38 on the inner edge of the magnet 52, the enlarged rim 40 on
the outside edge of the magnet 52, and the body of the two second pole
piece members 18 above and below the magnet 52 prevent the magnets 52 from
moving out of their stacked orientation by the repelling forces of
adjacent magnets.
As will be understood by a person skilled in the art, the various second
pole piece members 18 and corresponding magnets 52 cannot be alternately
stacked into the permanent magnet subassembly 70 unless the various second
pole piece members 18 are held together by a force that overcomes the
repulsive forces generated by the opposed magnets. In FIG. 6, the means
and method of alternately stacking the various pole pieces 12 and ring
magnets 14 around a TWT is shown.
Referring to FIG. 6, there is shown a lower fixture 74 into which are
placed the alternately stacked second pole piece members 18 and
corresponding magnets 52 so as to form a first semi-cylindrical permanent
magnet subassembly 70 of a desired length. The fixture 74 confines the
size of the permanent magnet subassembly 70 thereby preventing the
permanent magnet subassembly 70 from being distorted by the repulsive
forces of the various magnets 52. As has been previously explained, as the
various second pole piece members 18 are stacked, the central hubs 38 of
each adjacent second pole piece member 18 abut and the various center
reliefs 30 align, creating a single linear semicircular relief 73
extending across the length of the first permanent magnet subassembly 70
periodic gaps 72 are formed between each of the hubs 38 as a result of the
magnets 52 being interposed between each of the hubs 38.
An upper fixture 78 is connected to the lower fixture 74 so as to allow the
upper fixture 78 to be folded over the lower fixture 74. In the upper
fixture 78, the first pole piece members 16 and corresponding semicircular
magnets 50 are alternately stacked in the same manner previously described
in regard to the second pole piece members 18, so as to form a second
permanent magnet subassembly 80. When stacked, the hubs 36 of each of the
first pole piece members 16 and the various center reliefs 32 align,
creating a periodic semicircular relief 83 that extends across the entire
length of the second permanent magnet subassembly 80. Periodic gaps 82 are
formed between each of the hubs 36 as a result of the magnets 50 being
stacked between each of the hubs 36. The upper fixture 78 and the lower
fixture 74 are aligned so that the various male locking flanges 20 of the
first pole piece members 16 pass into the female receptacles 24 of the
second pole piece members 18 as the upper fixture 78 is folded atop the
lower fixture 74 and the first permanent magnet subassembly 70 engages the
second permanent magnet subassembly 80.
Prior to the second permanent magnet subassembly 80 of stacked first pole
piece members 16 being placed atop the first permanent magnet subassembly
70 of stacked second pole piece members 18, an electron beam device such
as a TWT 86 is placed between the first and second permanent magnet
subassemblies 70, 80. Typically, a TWT 86 is comprised of a cathode 88 and
collector 90 positioned at opposite ends of an evacuated tube 92. Within
the evacuated tube 92 is positioned a helix circuit or other slow wave
structure (not shown) having a signal input 94 and an signal output 96,
supported by rigid flange members 98, 100, respectively. The radius used
to create the semicircular reliefs 73, 83 in the first and second
permanent magnet subassemblies 70, 80, correspond to the radius of the
evacuated tube 92 used in the TWT 86. Consequently, the evacuated tube 92
of the TWT can be placed into the circular aperture formed by joining the
first permanent magnet subassembly 70 to the second permanent magnet
subassembly 80.
Typically, in a TWT, the PPM assembly extends the length of the TWT from
the signal input 94 to the signal output 96. As such, in the present
embodiment the length of the first permanent magnet subassembly 70 and the
length of the second permanent magnet subassembly 80 are chosen to
correspond to the length of the TWT evacuation tube 92 between the rigid
flange members 98, 100 that respectively support the signal input 94 and
the signal output 96.
To form the present invention PPM assembly around the shown TWT 86, the
evacuation tube 92 of the TWT 86 is placed within the semicircular relief
73 of the first permanent magnet subassembly 70. Once the TWT 86 is in
place, the upper fixture 78 is folded over the lower fixture 74 such that
the second permanent magnet subassembly 80 engages the first permanent
magnet subassembly 70 and the various male locking flanges 20 of the first
pole piece members 16 enter the female receptacles 24 of the second pole
piece members 18. Once properly positioned, the upper fixture 78 and the
lower fixture 74 are compressed toward one another by any known pressing
operation. The resulting compression forces the various male locking
flanges 20 to deform within the various female receptacles 24, thereby
permanently affixing the first permanent magnet subassembly 70 to the
second permanent magnet subassembly 80. By affixing the first permanent
magnet subassembly 70 to the second permanent magnet subassembly 80,
around the evacuated tube section of the TWT 86, the cylindrically-shaped
present invention PPM is formed.
As has been previously described, the length of both the first and second
permanent magnet assemblies 70, 80 is formed so as to correspond in length
with the length of the TWT evacuated tube 92 between the rigid flange
members 98, 100. Consequently, when the assembled PPM stack is removed
from the upper and lower fixture 78, 74 the rigid flange members 98, 100
contact the first and last magnet, preventing the formed PPM stack from
separating under the repulsive forces of the stacked ring magnets. By
forming the first and second permanent magnet assemblies 70, 80 by
stacking semicircular pole pieces and magnets. A cylindrical PPM can be
efficiently assembled around an election tube in a manner that is more
efficient and cost effective than existing prior art methods.
Additionally, the need for spacing elements and adhesive or tape is
removed from the PPM assembly procedure, thereby reducing the time and
handling required to manufacture the present invention PPM.
It will be understood that the embodiments described herein are merely
exemplary and that a person skilled in the art may make variations and
modifications without departing from the spirit and scope of the
invention. All such variations and modifications are intended to be
included within the scope of the invention as defined in the appended
claims.
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